[PATCH v3 12/33] exfat: use the generic emergency read-only state

[Christian Brauner <brauner@kernel.org>]

Set SB_STATE_EMERGENCY_RO instead of a private bit when an error makes
the filesystem read-only. exfat_emergency_state() keeps telling a
shutdown (EIO) and the emergency state (EROFS) apart so none of its
callers change. The VFS refuses the remount to read-write now so exfat
doesn't have to, and /proc/mounts shows the filesystem read-only again.

The VFS also refuses to freeze the superblock in that state. So
FS_IOC_SHUTDOWN with EXFAT_GOING_DOWN_DEFAULT or _FULLSYNC shuts down
without the freeze after an error, there's nothing left to sync anyway.

Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
 fs/exfat/exfat_fs.h | 13 ++-----------
 fs/exfat/misc.c     |  6 ++----
 fs/exfat/super.c    | 12 ++++++------
 3 files changed, 10 insertions(+), 21 deletions(-)

diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h
index c0e712d9083a0..ac138f1119886 100644
--- a/fs/exfat/exfat_fs.h
+++ b/fs/exfat/exfat_fs.h
@@ -123,7 +123,6 @@ enum {
 
 /* Superblock flags */
 #define EXFAT_FLAGS_SHUTDOWN	1
-#define EXFAT_FLAGS_EMERGENCY_RO	2	/* read-only after an error */
 
 struct exfat_dentry_namebuf {
 	char *lfn;
@@ -376,20 +375,12 @@ static inline int exfat_forced_shutdown(struct super_block *sb)
 	return test_bit(EXFAT_FLAGS_SHUTDOWN, &EXFAT_SB(sb)->s_exfat_flags);
 }
 
-static inline int exfat_emergency_ro(struct super_block *sb)
-{
-	return test_bit(EXFAT_FLAGS_EMERGENCY_RO, &EXFAT_SB(sb)->s_exfat_flags);
-}
-
-/*
- * Modifications are refused after a forced shutdown (-EIO) and after an error
- * with errors=remount-ro (-EROFS).
- */
+/* -EIO after a forced shutdown, -EROFS after an error with errors=remount-ro */
 static inline int exfat_emergency_state(struct super_block *sb)
 {
 	if (unlikely(exfat_forced_shutdown(sb)))
 		return -EIO;
-	if (unlikely(exfat_emergency_ro(sb)))
+	if (unlikely(sb_emergency_ro(sb)))
 		return -EROFS;
 	return 0;
 }
diff --git a/fs/exfat/misc.c b/fs/exfat/misc.c
index 56dcb93ce69e0..03c5c2b9a65ec 100644
--- a/fs/exfat/misc.c
+++ b/fs/exfat/misc.c
@@ -25,8 +25,7 @@
  */
 void __exfat_fs_error(struct super_block *sb, int report, const char *fmt, ...)
 {
-	struct exfat_sb_info *sbi = EXFAT_SB(sb);
-	struct exfat_mount_options *opts = &sbi->options;
+	struct exfat_mount_options *opts = &EXFAT_SB(sb)->options;
 	va_list args;
 	struct va_format vaf;
 
@@ -49,8 +48,7 @@ void __exfat_fs_error(struct super_block *sb, int report, const char *fmt, ...)
 		 */
 		if (!(sb->s_flags & SB_BORN))
 			sb->s_flags |= SB_RDONLY;
-		else if (test_and_set_bit(EXFAT_FLAGS_EMERGENCY_RO,
-					  &sbi->s_exfat_flags))
+		else if (!sb_set_emergency_ro(sb))
 			return;
 		exfat_err(sb, "Filesystem has been set read-only");
 	}
diff --git a/fs/exfat/super.c b/fs/exfat/super.c
index feeda41a80741..e3587ed270245 100644
--- a/fs/exfat/super.c
+++ b/fs/exfat/super.c
@@ -100,7 +100,7 @@ static int exfat_set_vol_flags(struct super_block *sb, unsigned short new_flags)
 	 * if this volume has been mounted with read-only,
 	 * or an error left it read-only (it stays dirty then)
 	 */
-	if (sb_rdonly(sb) || exfat_emergency_ro(sb))
+	if (sb_rdonly_any(sb))
 		return 0;
 
 	p_boot->vol_flags = cpu_to_le16(new_flags);
@@ -176,6 +176,11 @@ int exfat_force_shutdown(struct super_block *sb, u32 flags)
 	if (exfat_forced_shutdown(sb))
 		return 0;
 
+	/* After an error there is nothing to sync and freezing fails. */
+	if ((flags == EXFAT_GOING_DOWN_DEFAULT ||
+	     flags == EXFAT_GOING_DOWN_FULLSYNC) && sb_emergency_ro(sb))
+		flags = EXFAT_GOING_DOWN_NOSYNC;
+
 	switch (flags) {
 	case EXFAT_GOING_DOWN_DEFAULT:
 	case EXFAT_GOING_DOWN_FULLSYNC:
@@ -789,11 +794,6 @@ static int exfat_reconfigure(struct fs_context *fc)
 
 	fc->sb_flags |= SB_NODIRATIME;
 
-	/* After an error the filesystem stays read-only until unmount. */
-	if ((fc->sb_flags_mask & SB_RDONLY) && !(fc->sb_flags & SB_RDONLY) &&
-	    sb_rdonly(sb) && exfat_emergency_ro(sb))
-		return -EROFS;
-
 	sync_filesystem(sb);
 
 	if ((fc->sb_flags & (SB_FORCE | SB_RDONLY)) == SB_RDONLY &&

-- 
2.53.0